Graphene has a very high carrier mobility, making it a suitable material for use in high speed, high performance electronics. However, to attain optimal device performance, very high quality graphene is needed. For example, when graphene films are rough, or domains are small, carrier mobility will be reduced due to enhanced scattering. Producing high quality graphene using conventional techniques is very difficult. For example, one approach to forming graphene involves heating a silicon carbide surface to decompose the silicon carbide into silicon and carbon atoms. The silicon atoms evaporate leaving behind a carbon-rich surface which can orient itself into one or more graphene layers. With this approach, however, the resulting graphene layers have a rough surface morphology and thus may be unsuitable for high-performance device applications.
Such a conventional approach is depicted graphically in FIGS. 1A-B. Namely, in FIG. 1A, a silicon carbide wafer 102 is shown. For illustrative purposes, the silicon atoms are represented schematically with white boxes and the carbon atoms are represented schematically with black boxes. With any silicon carbide wafer there is going to be a certain degree of unevenness at the surface which is due to the inability to manufacture atomically-flat surfaces over wafer-scale dimensions. If the surface is not perfectly flat, it will have “atomic steps” defined by laterally undercoordinated silicon and/or carbon atoms.
As shown in FIG. 1B, when the surface of silicon carbide wafer 102 is heated the silicon atoms will evaporate leaving behind a carbon-rich surface arranged into one or more graphene layers 104. However, as illustrated in FIG. 1B, since the foundation for the graphene layers is an uneven surface, and the mobility of carbon and silicon atoms on the surface is relatively low when silicon carbide decomposes in vacuum, the graphene layers too will take on an uneven topology. Thus, the graphene layers formed will have a rough surface morphology.
Therefore, techniques for producing atomic step-free silicon carbide surfaces from which graphene layers can be formed would be desirable.